Three test tubes A, B and C each contain a different aqueous solution. Fig. 7.1 shows the colour of the solution in each tube. The three solutions are chose...
Question 1 Report
Three test tubes A, B and C each contain a different aqueous solution. Fig. 7.1 shows the colour of the solution in each tube. The three solutions are chosen from this list:
aqueous copper(II) sulfate aqueous iodine acidified potassium manganate(VII) aqueous potassium iodide
(a) Name the solution in each of the tubes A, B and C from their colours. [3]
(b) State which one of these solutions is an oxidising agent that turns from purple to colourless when it reacts. [1]
Answer Details
This question tests recognition of common laboratory solutions by their characteristic colours. Each of the listed solutions has a distinctive colour, so matching colour to identity is the skill.
(a) Naming the solutions from their colours [3]:
- The purple tube is acidified potassium manganate(VII) [1].
- The brown tube is aqueous iodine [1].
- The blue tube is (aqueous) copper(II) sulfate [1].
Aqueous potassium iodide is colourless, so it cannot be any of the three coloured tubes, which confirms the assignment.
(b) The oxidising agent that turns from purple to colourless when it reacts is acidified potassium manganate(VII) [1]. It oxidises other species while it is itself reduced from purple \(MnO_4^{-}\) to almost colourless \(Mn^{2+}\).
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